CN105745840A

CN105745840A - Elastic wave element, branching filter, and communication device

Info

Publication number: CN105745840A
Application number: CN201480063282.8A
Authority: CN
Inventors: 岸野哲也
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2013-11-29
Filing date: 2014-11-29
Publication date: 2016-07-06
Anticipated expiration: 2034-11-29
Also published as: CN105745840B; WO2015080278A1; JP6595659B2; US20160380176A1; JP6595342B2; US9978927B2; JPWO2015080278A1; JP2018139445A

Abstract

This elastic wave element is provided with a piezoelectric substrate (2), an excitation electrode (3) for emitting an elastic wave, the excitation electrode (3) being located on an upper surface (2A) of the piezoelectric substrate (2); and two reflectors (4) sandwiching the excitation electrode (3) in the direction of propagation of the elastic wave, the reflectors (4) being located on the upper surface (2A) of the piezoelectric substrate (2). The excitation electrode (3) has a main region (3a) located between both edges in the direction of propagation of the elastic wave and edge regions (3b) located on both sides of the main region (3a). 0.5*a*(m+1)<x<a*(m+1), where m is the number of electrode fingers in the edge regions (3b), a is the gap between electrode fingers in the main region (3a), and x is the gap between the electrode fingers in the main region (3a) facing the edge region (3b) and the electrode fingers of the reflector (4). The resonance frequency of the reflector (4) is lower than the resonance frequency of the main region (3a) of the excitation electrode (3).

Description

Elastic wave device, channel-splitting filter and communicator

Technical field

The present invention relates to elastic wave device, channel-splitting filter and communicator.

Background technology

In recent years, in the communicators such as mobile body terminal, in the channel-splitting filter that the signal sending from antenna/receiving is filtered, employ elastic wave device.Elastic wave device is made up of the exciting electrode of piezoelectric substrate He the interarea being formed at piezoelectric substrate.Elastic wave device utilization can make the characteristic that the signal of telecommunication and surface acoustic wave are changed mutually by the relation of exciting electrode and piezoelectric substrate.

Channel-splitting filter is by using multiple elastic wave devices, thus constituting such as receiving filter (Rx wave filter) or transmitting filter (with reference to TOHKEMY 2007-214902 publication etc.).Channel-splitting filter is by combining multiple elastic wave devices, thus setting frequency acceptance band or sending the passband of frequency band.

Summary of the invention

The problem that invention to solve

In such channel-splitting filter, the characteristic improved in the passband of frequency acceptance band or transmission frequency band is one of problem.

Therefore, the present invention makees in light of this situation, its object is to the elastic wave device of characteristic in a kind of passband that can improve signal of offer, channel-splitting filter and communicator.

For solving the means of problem

Elastic wave device involved by one embodiment of the present invention possesses piezoelectric substrate, exciting electrode and reflector.Described exciting electrode is positioned at the upper surface of described piezoelectric substrate, has multiple electrode and refers to, is used for producing elastic wave.Described reflector is positioned at the upper surface of described piezoelectric substrate, has multiple reflector electrode and refers to.This reflector is configured for 2 so that clip described exciting electrode on the direction of propagation of described elastic wave.Described exciting electrode has: be positioned at the main region that the electrode between the both ends on the direction of propagation of described elastic wave, described electrode refers to refers to that design is the same；With refer to, from electrode, the position that design is modulated with this main region continue to end, clip described main region and be positioned at 2 end regions of both sides.For described reflector, described reflector electrode the electrode referred to refers to than the electrode referred to by the described electrode of the described main region in described exciting electrode, the resonant frequency that design determines refers to that the resonant frequency that design determines is low.And, if the interval at the center that the center referred to by electrode described in described main region and the described electrode being adjacent refer to is set to a, the quantity that the described electrode constituting described end regions refers to is set to m, the described reflector electrode of the center that the described electrode near described end regions side among being referred to by the described electrode of described main region refers to and described reflector refer among the distance at center that refers to of the described reflector electrode near described end regions side be set to x, then meet 0.5 × a × (m+1) < x < a × (m+1).

Channel-splitting filter involved by one embodiment of the present invention possesses antenna terminal, is filtered and exports the transmitting filter of described antenna terminal and to receiving the receiving filter that is filtered of signal from described antenna terminal to sending signal, and described transmitting filter or described receiving filter have above-mentioned elastic wave device.

Communicator involved by one embodiment of the present invention possesses the above-mentioned channel-splitting filter that antenna is connected and the RF-IC electrically connected with this channel-splitting filter with this antenna electric.

Invention effect

According to the elastic wave device of the present invention, channel-splitting filter and communicator, it is possible to increase the characteristic in the passband of signal.

Accompanying drawing explanation

Fig. 1 indicates that the top view of the composition of the elastic wave device involved by one embodiment of the present invention.

Fig. 2 is equivalent to the section of the part cut off in the elastic wave device of Fig. 1 with Ic-Ic line.

Fig. 3 is by the amplification plan view that with a portion of amplification of IDT electrode in the elastic wave device of Fig. 1.

Fig. 4 is by the amplification plan view that with a portion of amplification of reflector in the elastic wave device of Fig. 1.

Fig. 5 is by the amplification plan view that with a portion of amplification of IDT electrode in the elastic wave device of Fig. 1.

Fig. 6 is the figure of the main region schematically showing Fig. 5 Elastic Wave resonance and the relation of the phase place in the repeated arrangement portion of end regions.

Fig. 7 has been by the result of the emulation of the elastic wave device involved by comparative example 1, and (b) is by the figure that with a portion of amplification of (a).

Fig. 8 has been by the result of the emulation of the elastic wave device involved by embodiment 1.

Fig. 9 has been by the result of the emulation of the elastic wave device involved by embodiment 1.

Figure 10 has been by the result of the emulation of the elastic wave device involved by comparative example 2, and (b) is by the figure that with a portion of amplification of (a).

Figure 11 has been by the result of the emulation of the elastic wave device involved by comparative example 3, and (b) is by the figure that with a portion of amplification of (a).

Figure 12 is the result that the position range to the change section realizing effect in the elastic wave device involved by embodiment 1 has emulated.

Figure 13 indicates that the top view of the variation (embodiment 2) of the elastic wave device involved by one embodiment of the present invention.

Figure 14 has been by the result of the emulation of the elastic wave device involved by embodiment 2.

Figure 15 is the result that the scope to the change section realizing effect in the elastic wave device involved by embodiment 2 has emulated.

Figure 16 is the schematic diagram that the communicator involved by one embodiment of the present invention is described.

Figure 17 is the circuit diagram that the channel-splitting filter involved by one embodiment of the present invention is described.

Figure 18 has been by the result of the emulation of the channel-splitting filter of Figure 14.

Figure 19 indicates that the major part enlarged drawing of the IDT electrode of the elastic wave device of Fig. 1 and a part for reflector electrode.

Figure 20 has been by the result of the emulation of the elastic wave device involved by embodiment 3, and (b) is by the figure that with a portion of amplification of (a).

Figure 21 has been by the result of the emulation of the elastic wave device involved by comparative example 3, and (b) is by the figure that with a portion of amplification of (a).

Figure 22 has been by the result of the emulation of the elastic wave device involved by comparative example 4, and (b) is by the figure that with a portion of amplification of (a).

Figure 23 has been by the result of the emulation of the elastic wave device involved by embodiment 3.

Figure 24 has been by the result of the emulation of the elastic wave device involved by embodiment 3.

Figure 25 has been by the result of the emulation of the elastic wave device involved by embodiment 4.

Detailed description of the invention

Hereinafter, about the elastic wave device involved by one embodiment of the present invention, channel-splitting filter and communicator, illustrate with reference to accompanying drawing.It addition, the figure used in the following description is schematic figure, the dimensional ratios on accompanying drawing etc. is not necessarily consistent with reality.

Above or below any direction can be set to by elastic wave device, but below, for convenience's sake, define orthogonal coordinate system xyz, and the positive side in z direction is set to top, use the term such as upper surface, lower surface.

Fig. 1 indicates that the top view of the composition of elastic wave (SAW:SurfaceAcousticWave) element 1 involved by one embodiment of the present invention.Fig. 2 is the sectional view of the part at the Ic-Ic cutting line place of Fig. 1.As it is shown in figure 1, SAW element 1 has piezoelectric substrate 2, is arranged at exciting electrode (IDT (InterdigitalTransducer, interdigital transducer) electrode) 3 and the reflector 4 of the upper surface 2A of piezoelectric substrate 2.

By the electrode of 2 the end regions 3b being positioned at reflector 4 side among IDT electrode 3, SAW element 1 refers to that the electrode of design and reflector 4 refers to design, it is possible to increase the characteristic of the passband of signal.Hereinafter, it is described in detail for each constitutive requirements.

Piezoelectric substrate 2 is by by Lithium metaniobate (LiNbO₃) crystal or lithium tantalate (LiTaO₃) substrate of the monocrystalline with piezoelectricity that constitutes of crystal and constitute.Specifically, for instance, the LiTaO that piezoelectric substrate 2 is cut by 36 °～48 ° Y-X₃Substrate is constituted.Can suitably set flat shape and the various sizes of piezoelectric substrate 2.As an example, the thickness (z direction) of piezoelectric substrate 2 is 0.2mm～0.5mm.

As it is shown in figure 1, IDT electrode 3 has the 1st comb electrodes 30a and the 2nd comb electrodes 30b.It addition, in the following description, sometimes by the 1st comb electrodes 30a and the 2nd comb electrodes 30b referred to as comb electrodes 30, they are not distinguish between.

As it is shown in figure 1, comb electrodes 30 has: 2 busbars 31 opposite each other and the multiple electrodes extended to other busbar 31 sides from each busbar 31 refer to 32.And, 1 pair of comb electrodes 30 is configured to the 1st electrode and refers to that 32a and the 2 electrode refers to that 32b is engaged with each other (intersection) on the direction of propagation of elastic wave.It addition, on busbar 31, it is also possible to configuration refers to 32 opposed dummy electrodes with electrode.Present embodiment is the situation being configured without dummy electrode.

Elastic wave produces on 32 orthogonal directions referring to multiple electrodes, and propagates.Therefore, after the crystal orientation of piezoelectric substrate 2 is taken in, 2 busbars 31 are configured to opposite each other with on the direction wanting to make the direction of elastic wave propagation to intersect.Multiple electrodes refer to that 32 are formed as upwardly extending in the side orthogonal relative to the direction wanting to make elastic wave propagation.Although it addition, the direction of propagation of elastic wave by multiple electrodes refer to 32 towards etc. determine, but in the present embodiment, for convenience's sake, sometimes with the direction of propagation of elastic wave for benchmark, illustrate multiple electrode refer to 32 towards etc..

Busbar 31 is for example formed as the strip linearly extended with approximately fixed width.Therefore, the edge of the side relative to each other of busbar 31 is linearity.Multiple electrodes refer to that 32 for example formed as the strip linearly extended with approximately fixed width, is spaced according to approximately fixed on the direction of propagation of elastic wave.

As it is shown in figure 1, in IDT electrode 3, on the direction of propagation of elastic wave, be set with the main region 3a being configured at go-and-retum and from two ends to 2 end regions 3b of main region 3a.Constitute multiple electrodes of a pair comb electrodes 30 of the main region 3a of IDT electrode 3 and refer to that 32 are set as that adjacent electrode refers in the width of 32 that interval in the heart becomes the 1st spacing Pt1a.1st spacing Pt1a is in main region 3a, for instance be set as equal with wanting the half-wavelength that the wavelength X of the elastic wave under the frequency of resonance occurs.Wavelength X (2 × Pt1a) is such as 1.5 μm～6 μm.Refer at this 1st spacing Pt1a, as it is shown on figure 3, on the direction of propagation of elastic wave, refer to from the 1st electrode 32a width center to and the 1st electrode refer to that the 2nd adjacent for 32a electrode refers to the interval at the center of the width of 32b.Hereinafter, when spacing is described, sometimes by " electrode refers to that the " center " of width of 32 is referred to as " electrode refers to that the " center " of 32 illustrates.

The width w1 that each electrode refers on the direction of propagation of the elastic wave of 32 is set appropriately according to the electrical characteristic etc. required for SAW element 1.Electrode refers to that the width w1 of 32 is such as 0.3 times～0.7 times of the 1st spacing Pt1a.

Multiple electrodes refer to that the length (from busbar 31 to the length of front end) of 32 is such as set at essentially identical length.Alternatively, it is also possible to change each electrode to refer to the length of 32, for instance can also go forward along with the direction of propagation in elastic wave and then increase or shorten.Specifically, it is also possible to by making each electrode refer to, the length of 32 changes relative to the direction of propagation and constitutes the IDT electrode 3 of apodization type.In the case, it is possible to reduce the parasitism (spurious) of transverse mode or improve resistance to electric power.

IDT electrode 3 is such as consisted of the conductive layer 15 being made up of metal.As this metal, it is possible to list such as Al or the alloy (Al alloy) being main component with Al.Al alloy is such as made of Al-Cu alloy.It addition, IDT electrode 3 can also be made up of multiple metal levels.The various sizes of IDT electrode 3 are set appropriately according to the electrical characteristic etc. required for SAW element 1.The thickness (z direction) of IDT electrode 3 is such as 50nm～600nm.

IDT electrode 3 both can directly be configured at the upper surface 2A of piezoelectric substrate 2, it is also possible to be configured at the upper surface 2A of piezoelectric substrate 2 via other components.These other components are such as made up of Ti, Cr or their alloy etc..When IDT electrode 3 is configured at the upper surface 2A of piezoelectric substrate 2 via other components, the thickness of these other components is set as thickness (for the thickness of the 5% of the thickness of IDT electrode 3 when being such as made up of) to the degree that the electrical characteristic of IDT electrode 3 impacts hardly Ti.

Additionally, refer on 32 at the electrode constituting IDT electrode 3, in order to improve the temperature characterisitic of SAW element 1, it is also possible to stacking quality supplement film.As quality supplement film, it is possible to use such as SiO₂Deng.

If IDT electrode 3 is applied in voltage, then near the upper surface 2A of piezoelectric substrate 2, encourage the elastic wave propagated in the x-direction.The elastic wave that obtains of excitation is at the reflection at borders of the non-configuring area region of the strip between 32 (the adjacent electrode refer to) referring to 32 with electrode.Then, formed and refer to, with the electrode of main region 3a, the standing wave that the 1st spacing Pt1a of 32 is half-wavelength.Standing wave is converted into and the signal of telecommunication of this standing wave same frequency, refers to that 32 are removed by electrode.In this way, SAW element 1 plays a role as single port resonator.

Reflector 4 is formed as multiple reflector electrode and refers to become between 42 slit-shaped.That is, reflector 4 has: reflector busbar 41 opposite each other on the direction intersected with the direction of propagation of elastic wave；And upwardly extend so that the multiple reflector electrodes being connected with each other by busbar 41 refer to 42 in the side orthogonal with the direction of propagation of elastic wave between these busbars 41.Reflector busbar 41, for example formed as the strip linearly extended with approximately fixed width, configures abreast with the direction of propagation of elastic wave.The interval that the adjacent interval between reflector busbar 41 such as can be set as between the adjacent busbar 31 of IDT electrode 3 is roughly the same.

Multiple reflector electrodes refer to that the spacing Pt2 of reflection occurs 42 elastic waves being configured to make to be encouraged by IDT electrode 3.Described below about spacing Pt2.Referring to from Pt2 here, as shown in Figure 4, in the propagation direction, center that reflector electrode refers to 42 and the reflector electrode being adjacent refer to the interval at the center of 42.

Additionally, multiple reflector electrodes refer to 42 strips being formed as linearly extending with approximately fixed width.Reflector electrode refers to that the width w2 of 42 such as can be set as referring to that with electrode the width w1 of 32 is identical.Reflector 4 is such as formed by the material identical with IDT electrode 3, and is formed as the thickness equal with IDT electrode 3.

As in figure 2 it is shown, protective layer 5 covers, IDT electrode 3 and reflector 4 are arranged on piezoelectric substrate 2.Specifically, protective layer 5 covers IDT electrode 3 and the surface of reflector 4, and covers the part exposed in the middle of upper surface 2A from IDT electrode 3 and reflector 4.The thickness of protective layer 5 is such as 1nm～50nm.

Protective layer 5 is made up of the material with insulating properties, contributes to protection IDT electrode 3 and reflector 4 not by corrosion etc..Preferably, if protective layer 5 is risen by temperature, the SiO that the spread speed of elastic wave is accelerated₂Formed Deng material, thus can also the change of electrical characteristic caused for the change of the temperature of elastic wave device 1 be suppressed less.

In the SAW element 1 of such composition, the electrode being positioned at the end regions 3b of end side compared with main region 3a refers to that the electrode of design and reflector 4 refers to design following setting.

(I) about the end regions 3b of IDT electrode 3

IDT electrode 3 possesses main region 3a and end regions 3b.It is the same that the electrode of main region 3a refers to design, and its electrode refers to that design determines the driving frequency of IDT electrode 3 entirety.That is, coordinate desired driving frequency, carried out referring to electrode that spacing, width, the design parameter such as the thickness electrode that is set to fix of 32 refer to design.End regions 3b refers to since the same electrode of this main region 3a refers to that designing the part being modulated acts the region continuing to end.At this, so-called " being modulated " refers to, make electrode refer to 32 spacing (electrode refers in 32 interval in the heart), gap (electrode refers to the gap between 32), width, thickness design parameter at least 1 change.The electrode constituting main region 3a refers to that the radical of 32 and the electrode of composition end regions 3b refer to that the radical of 32 suitably sets, so that being referred to that the resonant frequency of design determines the driving frequency of IDT electrode 3 entirety by the electrode based on main region 3a.Specifically, as long as the electrode constituting main region 3a being referred to the radical of 32 sets to refer to that the radical of 32 is many than the electrode constituting end regions 3b.

The major part amplification view of IDT electrode 3 shown in Figure 19 and reflector 4.At this, the electrode near end regions 3b side in main region 3a is referred to, and 32 are set to electrode and refer to A, the electrode being adjacent is referred to, and the electrode near main region 3a side in 32 i.e. end regions 3b refers to that 32 are set to electrode and refer to B, the reflector electrode near IDT electrode 3 side in reflector 4 is referred to, and 42 are set to reflector electrode and refer to C.In addition, if the center that the electrode in main region 3a refers to the width of 32 and the electrode being adjacent refer to that the interval at the center of the width of 32 is set to a (aforesaid 1st spacing Pt1a), the electrode constituting end regions 3b is referred to that the radical of 32 is set to m, electrode referring to, center and the reflector electrode of the width of A refer to that the distance at the center of the width of C is set to x, then x becomes more than 0.5 × a × (m+1) and the value less than a × (m+1).

By such composition, thus with between main region 3a with end regions 3b not modulator electrode refer to design and end regions 3b become the same situation compared with can reduce electrode and refer to that A and reflector electrode refer to the distance of C.Thereby, it is possible to make the electrode of the IDT electrode 3 in end regions 3b refer to, the part (hereinafter sometimes referred to as aligning section) of 32 repeated arrangement is close to main region 3a side.As a result, it is possible to make the boundary condition of the IDT electrode 3 of generation elastic wave change, it is possible to suppress the generation of longitudinal mode.

For meet such condition make electrode refer to A and reflector electrode refer to that the concrete example that the distance of C changes illustrates.Such as, as it is shown in figure 5, pass through to make to refer to that 32a and the 2nd electrode refer to that the clearance G p in the gap of 32b changes as the 1st adjacent electrode such that it is able to A and reflector electrode refer to that the distance of C changes to make electrode refer to.Specifically, in order to make the electrode of end regions 3b refer to, the aligning section entirety of 32 shifts relative to main region 3a, as long as referring to that A refers to that with electrode the 2nd clearance G p2 in the gap of B is set as that the adjacent electrode being used in main region 3a refers to that the 1st clearance G p1 in the gap between 32 (the 1st electrode refers to that 32a and the 2nd electrode refer to 32b) is little as electrode.The 2nd clearance G p2 less for clearance G p1 than the 1st becomes change section 300.

At this, the repeated arrangement for IDT electrode 3 is studied.As shown in Figure 6, the electrode of IDT electrode 3 refers to that the repeated arrangement of 32 refers to and such as refers to the center of 32a with the 1st electrode and clip the 2nd electrode and refer to that 32b is positioned at the 1st electrode on side and refers to the arrangement that the center of 32a was repeated for 1 cycle.It addition, Fig. 6 sets the 2nd electrode to refer to that the center of 32b becomes an example of maximum displacement.Assuming that the repetition period produced by such repeated arrangement.

In fig. 6 it is shown that the repeated arrangement of the IDT electrode 3 of main region 3a to be maintained the setting that original cycle extends to end side and the setting extended in repeated arrangement maintenance original cycle of the IDT electrode 3 of end regions 3b to main region 3a side.Relatively these 2 repeated arrangement.Compared with the phase place of the phase place of the repeated arrangement of the IDT electrode 3 of end regions 3b assumed repetition period repetition period assumed with the repeated arrangement by the IDT electrode 3 in main region 3a, there occurs displacement to main region 3a side.By this composition such that it is able to make the boundary condition of the IDT electrode 3 of generation elastic wave change, it is possible to suppress the generation of longitudinal mode.

(II) design is referred to about the electrode of reflector

Except above-mentioned electrode refers to the setting that A and reflector electrode refer to C and position relationship, also will be referred to that the resonant frequency that design determines is set to the electrode than the main region 3a by IDT electrode 3 and refers to that the resonant frequency of design decision is low by the electrode of reflector 4.If the resonant frequency of reflector 4 reduces spacing Pt2, raising, if expanding spacing Pt2, reducing.Therefore, in order to make the resonant frequency of reflector 4 resonant frequency lower than the main region 3a of IDT electrode 3, the reflector electrode of reflector 4 is referred to the spacing Pt2 of the 42 spacing Pt (the 1st spacing Pt1a) being set greater than in the main region 3a of IDT electrode 3.

At this, A and reflector electrode refer to that the distance of C changes to make electrode refer in the present embodiment, in order to confirm the effect that the resonant frequency of reflector 4 is set as the SAW element of setting, have carried out the emulation of the frequency characteristic of SAW element.First, the condition as comparative example 1, existing SAW element emulated is as follows.

(simulated conditions of comparative example 1)

[piezoelectric substrate 2]

Material: 42 ° of Y cut X and propagate LiTaO₃Substrate

[IDT electrode 3]

Material: made of Al-Cu alloy (but, between piezoelectric substrate 2 and conductive layer 15, there is the basal layer being made up of Ti of 6nm.)

Thickness (made of Al-Cu alloy layer): 324nm

The electrode of IDT electrode 3 refers to 32:

Radical: 100

1st spacing Pt1a:2.19 μm

Dutycycle (w1/Pt1): 0.5

Cross width W:65.7 μm (15 λ)

[reflector 4]

Thickness (made of Al-Cu alloy layer): 324nm

Reflector electrode refers to the radical of 42: 30

Reflector electrode refers to spacing Pt2:2.19 μm (Pt1a × 1.00) of 42

[protective layer 5]

Material: SiO₂

Thickness: 15nm

The result of the SAW element of the comparative example 1 calculated according to the condition of such emulation shown in Fig. 7.Curve chart shown in Fig. 7 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.Additionally, Fig. 7 (b) is the figure part surrounded by the single dotted broken line of Fig. 7 (a) being exaggerated.From this result, before and after the 890MHz of frequency low for about 900MHz being used for resonant frequency, parasitism is created.To this, it is believed that the parasitism creating the big reflector mode of oscillation intensity change in SAW element in reflector is one of reason.

Then, the situation of effect is realized by emulating the SAW element (embodiment 1) confirmed involved by present embodiment.Below, it is shown that the condition of the SAW element (embodiment 1) involved by present embodiment.It addition, following condition only illustrates the difference of the SAW element with comparative example 1.

(simulated conditions of embodiment 1)

[IDT electrode 3]

The electrode of IDT electrode 3 refers to 32:

The position of the 2nd clearance G p2: between (from the end of IDT electrode 3) the 8th and the 9th

2nd clearance G p2: the 1 clearance G p1 × 0.90

[reflector 4]

Reflector electrode refers to spacing Pt2: the 1 spacing Pt1a × 1.02 of 42

The result of the SAW element of the embodiment 1 calculated according to the condition of such emulation shown in Fig. 8.Curve chart shown in Fig. 8 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.Additionally, Fig. 8 (b) is the figure part surrounded by the single dotted broken line of Fig. 8 (a) being exaggerated.

From this result, there is change section 300 by being positioned at the end regions 3b of end side compared with main region 3a such that it is able to reduce the parasitism of reflector mode, and reduce the parasitism of the impedance produced before and after 890MHz in comparative example 1.Additionally in this embodiment, from the end of IDT electrode 3, comprise 8 electrodes refer to, constitute end regions 3b in the region nearby referred to the 9th electrode.

Then, the optimum about the 2nd clearance G p2 has emulated.The condition of emulation is all identical except making the 2nd gap (Gp2) of the above embodiments 1 change.This result shown in Fig. 9.

Curve chart shown in Fig. 9 is transverse axis is the 2nd clearance G p2, and the longitudinal axis is the parasitic maximum phase peak value outside passband.At this, so-called maximum phase peak value refers to, the value of the maximum parasitic phase place outside expression passband, and then parasitic meeting more big with the difference of-90deg is more big.In fig .9, with the maximum phase peak value of comparative example 1 shown in phantom extended in parallel with transverse axis.From the result shown in Fig. 9 it can be seen that by the 2nd clearance G p2 being set as relative to the 1st clearance G p1 be more than 0.87 times and less than 1 times, thus realizing the effect above.Additionally, from the result shown in Fig. 9 it can be seen that maximum phase peak value (the result shown in Fig. 9 corresponding with-90deg) owing to can eliminate parasitism substantially when the 2nd clearance G p2 being set to 0.90 times of the 1st clearance G p1, therefore, it is possible to parasitism is greatly reduced.

And then in order to confirm the effect of the SAW element (embodiment 1) involved by present embodiment, for relative to comparative example 1, (I) has and is set as that the situation (comparative example 3) of setting has emulated in the situation (comparative example 2) of end regions comprising change section near end side compared with main region 3a and the resonant frequency of (II) only reflector.In other words, in comparative example 2, the resonant frequency of reflector is equal with main region 3a, and the electrode that IDT electrode 3 is all the same in comparative example 3 refers to design.The corresponding table of embodiment 1 shown in table 1 and comparative example 1～3.

[table 1]

In Table 1, the hurdle of the 2nd clearance G p2 illustrates the multiplying power relative to the 1st clearance G p1.Specifically, the 2nd clearance G p2 of the SAW element of comparative example 2 is set as 0.90 times relative to the 1st clearance G p1.Additionally, in Table 1, the hurdle of the spacing Pt2 of reflector 4 illustrates the multiplying power of the 1st spacing Pt1a relative to IDT electrode 3.

The result emulated according to the condition of the SAW element of comparative example 2 shown in Figure 10, has illustrated the result that the condition of the SAW element according to comparative example 3 has emulated in Figure 11.Curve chart shown in Figure 10 and Figure 11 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.

As shown in the SAW element of comparative example 2, when only using when being set as setting as the clearance G p2 of change section 300, as shown in Figure 10, although the parasitism before and after the 890MHz that the SAW element at comparative example 1 produces can be reduced, but near the 895MHz near resonant frequency, create bigger parasitism.This may be considered owing to creating the vibration mode (so-called longitudinal mode) along the direction of propagation of elastic wave with multiple peak value in IDT electrode 3.

On the other hand, as shown in the SAW element of comparative example 3, when only the resonant frequency of reflector being set as setting, known as shown in figure 11, although the parasitism of reflector mode before and after the 890MHz that the SAW element at comparative example 1 produces can be reduced, but near 893MHz, create new parasitism (being estimated to be the parasitism of longitudinal mode).

In sum, SAW element according to present embodiment, by (I) being comprised the design being set to regulation compared with main region 3a near the end regions 3b of change section 300 of end side and the resonant frequency of (II) reflector, it is thus possible to reduce the parasitism of reflector mode, and the parasitism of longitudinal mode can be reduced, therefore, it is possible to reduce the parasitism produced in the frequency lower than passband.

Additionally, lower than the resonant frequency in main region 3a by the resonant frequency of reflector 4 is set as such that it is able to make the reflection frequency domain of reflector 4 be shifted over to the lower frequency side lower than the resonant frequency in main region 3a.Therefore, when the frequency low with the resonant frequency than main region 3a makes SAW element 1 perform action, it is possible to prevent from revealing from reflector 4 in the main region 3a elastic wave produced.Thereby, it is possible to the loss reduced under the frequency that the resonant frequency than main region 3a is low.

According to result above, shown in Figure 16 as be described hereinafter, in filter characteristic, it is possible to improve fluctuation and the loss in passband center portion, it is possible to increase frequency acceptance band or the characteristic in transmission frequency band.

And then, although the electrode becoming change section being referred to that A and electrode refer to that the change section in the gap of B is set in from end between the 8th and the 9th in the SAW element 1 of the above embodiments 1, even if but having carried out changing the research of the scope that this setting also realizes the effect above.Specifically, in the SAW element of embodiment 1, A and electrode refer to that the position of B changes and have emulated to make electrode refer to.The result of this emulation shown in Figure 12.In curve chart shown in Figure 12, transverse axis radical m (between m root and m+1 root) from end represents that electrode refers to the position of B, and the longitudinal axis is parasitic maximum phase peak value.Maximum phase peak value in parallel with the transverse axis SAW element of comparative example 1 shown in phantom in the plot.It addition, for each radical m, have adjusted the 2nd clearance G p2 and make the maximum phase peak value of parasitism become minimum.In other words, in fig. 12, the minima of the maximum phase peak value of parasitism is illustrated for each radical m.

From this result, if radical m is set to more than 70, then parasitic maximum phase peak value can become worse compared to comparative example 1, therefore by making radical m realize the effect above less than 70.From this result, when radical m is 8, it is possible to make the maximum phase peak value of parasitism become-90deg, therefore, it is possible to parasitism is greatly reduced.

On the other hand, even if from the result shown in Figure 12 it can be seen that when radical m is 0, also be able to reduce parasitic maximum phase peak value compared with the SAW element of comparative example 1.It addition, when radical m is 0, is that the interval making IDT electrode 3 and reflector 4 there occurs change to reducing direction, is be absent from electrode at end regions 3b to refer to the situation of 32.Even if B and reflector electrode refer to that the interval of C is more nearly than original interval in this case, electrode also to be made to refer to.According to above result, when representing, with the radical m from end, the position that electrode refers to B, it is achieved the change section in the gap of the effect above is set as the scope of 0≤m < 70.

It addition, in above-mentioned example, in IDT electrode 3, electrode refers to that designing the part being modulated is only the 2nd clearance G p2.That is, adjacent in end regions 3b electrode refers to that the gap of 32 is equal with the 1st clearance G p1, and electrode finger width, electrode dinger thickness degree and spacing are equal with main region 3a.So, by making the electrode of end regions 3b refer to, the configuration of 32 and the electrode of main region 3a refer to that the configuration of 32 is close such that it is able to suppress loss or the leakage of surface wave unintentionally.Additionally, by reducing the part that gap diminishes such that it is able to suppress resistance to electric power to decline.

(control electrode and refer to that A and reflector electrode refer to the additive method 1 of the distance of C)

In above-mentioned example, the electrode as the end regions 3b of IDT electrode 3 refers to that design describes the 2nd clearance G p2 of IDT electrode 3 method changed that makes but it also may the width w1a of 32 changes as change section 300 to make the electrode of IDT electrode 3 refer to.

Specifically, as shown in figure 13, for change section 300, electrode being referred to, the width w1a of 32 (electrode refers to B) is set as referring to that the width w1 of 32 is little than the electrode in main region 3a, and the 2nd clearance G p2 is set as identical with the 1st clearance G p1.By such setting, it is also possible to make the aligning section entirety of the IDT electrode 3 of close end side compared with change section 300 be shifted over to the aligning section side of the IDT electrode 3 in main region 3a.

In the case, compared with referring to A with electrode, the region near end side becomes end regions 3b, and end regions 3b comprises change section 300.

Even if by emulate confirm when so make electrode refer to the width w1a of 32 there occurs change present embodiment involved by SAW element (embodiment 2) also realize the situation of effect.The condition of the emulation of SAW element involved by embodiment 2 is shown.It addition, following condition only illustrates the difference of the SAW element with comparative example 1.

(simulated conditions of embodiment 2)

[IDT electrode 3]

The electrode of IDT electrode 3 refers to 32:

The position of change section 300 position of B (electrode refer to): (from the end of IDT electrode 3) the 9th

The electrode of change section 300 refers to that the electrode of width w1a: main region 3a of 32 refers to width w1 × 0.90 of 32

[reflector 4]

Reflector electrode refers to spacing Pt2: the 1 spacing Pt1a × 1.02 of 42

The result of the SAW element of the embodiment 2 calculated according to the condition of such emulation shown in Figure 14.Curve chart shown in Figure 14 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.Additionally, Figure 14 (b) is the figure part surrounded by the single dotted broken line of Figure 14 (a) being exaggerated.It addition, 1 electrode that this emulation is the IDT electrode 3 making to be positioned at end side compared with main region 3a refers to that the width w1a of 32 (electrode refers to B) there occurs the situation of change.

Even if when so make the electrode of IDT electrode 3 refer to as change section 300 the width w1a of 32 there occurs change, it is also possible to similarly to Example 1, reduce the parasitism of longitudinal mode, and reduce the parasitism of impedance produced before and after 890MHz in comparative example 1.

And then, the width w1a of 32 changes to make electrode refer to, the scope relative to comparative example 1 with effect has been emulated.Its result shown in Figure 15.In fig .15, transverse axis represents that the electrode relative to main region 3a refers to that the electrode of the width of 32 refers to the width (w1a/w1) of B (electrode of change section 300 refers to 32), and the longitudinal axis is parasitic maximum phase peak value.Additionally, with the maximum phase peak value in parallel with the transverse axis SAW element of comparative example 1 shown in phantom.

From this result, by electrode being referred to the width w1a of 32 is set as that the electrode relative to main territory 3a refers to that the width w1 of 32 is more than 0.877 times and less than 1 times, thus compared to the more effective fruit of comparative example 1.

(control electrode and refer to that A and reflector electrode refer to the additive method 2 of the distance of C)

In the above embodiments 1 and embodiment 2, refer to that A and electrode refer to the gap of B or adjust electrode and refer to the width of B by adjusting electrode, so that electrode refers to that A and reflector electrode refer to that the distance of C meets desired condition but it also may by making the resonant frequency being referred to design decision by the electrode of end regions 3b refer to that the resonant frequency that design determines realizes higher than by the electrode of main region 3a.

The resonant frequency of the IDT electrode 3 being positioned at main region 3a and end regions 3b can bring it about change by the spacing Pt1 of adjustment IDT electrode 3.Specifically, as long as reducing spacing Pt1 to improve resonant frequency, as long as expanding spacing Pt1 to reduce resonant frequency.Therefore, in IDT electrode 3, in order to the resonant frequency of main region 3a is set as that the resonant frequency than end regions 3b is low, as long as the 1st spacing Pt1a is set as wider than the 2nd spacing Pt1b.

In order to confirm the effect that as in this embodiment resonant frequency of IDT electrode 3 and reflector 4 is set as the SAW element of setting, carry out the emulation of the frequency characteristic of SAW element.

Then, it is shown that the condition of the SAW element (embodiment 3) involved by present embodiment.It addition, following condition only illustrates the difference of the SAW element with above-mentioned comparative example 1.

(simulated conditions of embodiment 3)

[IDT electrode 3]

The electrode of IDT electrode 3 refers to 32:

The electrode of end regions 3b refers to the radical of 32: (from the end of IDT electrode 3) 12 the 2nd spacing Pt1b: the 1 spacing Pt1a × 0.990

[reflector 4]

Reflector electrode refers to spacing Pt2: the 1 spacing Pt1a × 1.02 of 42

The result of the SAW element involved by present embodiment calculated according to the condition of such emulation shown in Figure 20.Curve chart shown in Figure 20 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.It addition, the present embodiment 3 is to will be located in the IDT electrode 3 of end regions 3b to be all set to the situation of the 1st spacing Pt1a.Figure 20 (b) is the figure being exaggerated at the position surrounded by the single dotted broken line of Figure 20 (a).From this result, it is possible to reduce the parasitism produced before and after 890MHz in comparative example 1.

And then in order to confirm the effect of the SAW element (embodiment 3) involved by present embodiment, carried out the emulation applying following situation respectively: the resonant frequency of end regions 3b is only set as the situation of setting by (I) as comparative example 4；As comparative example 5, the resonant frequency of reflector is only set as the situation of setting by (II).In other words, in comparative example 4, the resonant frequency of reflector is equal with the main region 3a of IDT electrode 3, and in comparative example 5, the electrode of IDT electrode 3 refers to that design is all the same.The corresponding table of embodiment 3 shown in table 2 and comparative example 1,4,5.

[table 2]

In table 2, the hurdle of the 2nd spacing Pt1b illustrates the multiplying power relative to the 1st spacing Pt1a.Specifically, the 2nd spacing Pt1b is set as 0.990 times relative to the 1st spacing Pt1a by the SAW element of comparative example 4.Additionally, in table 2, the hurdle of the spacing Pt2 of reflector 4 illustrates the multiplying power of the 1st spacing Pt1a relative to IDT electrode 3.

The result emulated according to the condition of the SAW element of comparative example 4 shown in Figure 21, the result emulated according to the condition of the SAW element of comparative example 5 shown in Figure 22.Curve chart shown in Figure 21 and Figure 22 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.

As shown in the SAW element of comparative example 4, when only the resonant frequency of end regions being set as setting, as shown in figure 21, although the parasitism before and after the 890MHz that the SAW element at comparative example 1 produces can be reduced, but near the 895MHz near resonant frequency, create bigger parasitism.

On the other hand, as shown in the SAW element of comparative example 5, when only the resonant frequency of reflector being set as setting, known as shown in figure 22, although the parasitism before and after the 890MHz that the SAW element at comparative example 1 produces can be reduced, but near 890MHz, create new parasitism (being estimated to be the parasitism of longitudinal mode).

In sum, SAW element according to present embodiment, by the resonant frequency of the resonant frequency of (I) end regions 3b and (II) reflector is set as setting, it is thus possible to reduce the parasitism of reflector mode, and the parasitism of longitudinal mode can be reduced, therefore, it is possible to reduce the parasitism produced in the frequency lower than passband.

Then, the optimum about the 2nd spacing Pt1b has emulated.The condition of emulation is as follows.It addition, following condition only illustrates the difference of the SAW element with comparative example 1.

(condition of the optimum of the 2nd spacing Pt1b of embodiment 3)

[IDT electrode 3]

Radical: 200

[reflector 4]

Spacing Pt2: the 1 spacing Pt1a × 1.02

In such a situa-tion, make the 2nd spacing Pt1b change to have calculated.This result shown in Figure 23.In curve chart shown in Figure 23, transverse axis is the 2nd spacing Pt1b, and the longitudinal axis is the parasitic maximum phase peak value outside passband.Additionally, with the maximum phase peak value in parallel with the transverse axis SAW element of comparative example 1 shown in phantom.

From the result shown in Figure 23 it can be seen that be set as that relative to the 1st spacing Pt1a be more than 0.986 times and less than 1 times by the 2nd spacing Pt1b, thus realizing the effect above.Additionally, from the result shown in Figure 23 it can be seen that due to when the 2nd spacing Pt1b is set to 0.991 × Pt1a, it is possible to eliminate the maximum phase peak value (corresponding with-90deg in the result shown in Figure 23) of parasitism substantially, therefore, it is possible to parasitism is greatly reduced.

Although additionally, end regions 3b is set as 12 from the end of IDT electrode 3 in the SAW element of the above embodiments 3, even if but having carried out changing the research that the setting of this end regions 3b also realizes the scope of the effect above.Specifically, in the SAW element of embodiment 3, making the electrode of end regions 3b refer to, the radical of 32 changes has emulated.The result of this emulation shown in Figure 24.In curve chart shown in Figure 24, transverse axis is the radical m that the electrode of end regions 3b refers to 32, and the longitudinal axis is parasitic maximum phase peak value.It addition, for each radical m, have adjusted the 2nd spacing Pt1b and make the maximum phase peak value of parasitism become minimum.In other words, in fig. 24, the minima of the maximum phase peak value of parasitism is illustrated for each radical m.

From this result, if the radical m of end regions 3b is set to more than 70, then parasitic maximum phase peak value can become worse compared to comparative example 1, therefore by making radical m realize the effect above less than 70.From this result, when radical m is 12, it is possible to make the maximum phase peak value of parasitism become-90deg, therefore, it is possible to parasitism is greatly reduced.On the other hand, as can be seen from Figure 24, even if when radical m is 0, it also is able to reduce parasitic maximum phase peak value compared with the SAW element of comparative example 1.It addition, when so-called radical m is 0, be the situation making the interval of IDT electrode 3 and reflector 4 there occurs change.According to above result, the electrode of the end regions 3b in SAW element 1 refers to that the radical m of 32 is set as the scope of 0≤m < 70.

(resonant frequency of end regions is set as the additive method of setting)

As the method that the resonant frequency of the end regions 3b of IDT electrode 3 is set as setting, describe and make the 2nd spacing Pt1b of IDT electrode 3 method changed but it also may make the dutycycle being positioned at the IDT electrode 3 of end regions 3b change.

As it is shown on figure 3, the dutycycle of IDT electrode 3 is the width w1 that the 2nd electrode refers to 32b divided by referring to that the 1st electrode of side of 32b refers to that the end of 32a refers to the distance Dt1 of the end of the opposite side of 32b and the value that obtains to the 2nd electrode from the 2nd electrode on the direction of propagation of elastic wave.When so changing electrode and referring to the dutycycle of 32 to make the resonant frequency of end regions 3b change, as long as reducing dutycycle to improve the resonant frequency of IDT electrode 3, as long as increasing dutycycle to reduce the resonant frequency of IDT electrode 3.Therefore, it is positioned at the IDT electrode 3 of end regions 3b to be set as than its dutycycle dutycycle less than the IDT electrode 3 being positioned at main region 3a.

Even if also realize the situation of effect by emulating the SAW element (embodiment 4) confirmed when so making dutycycle there occurs change involved by present embodiment.Then, it is shown that the condition of the emulation of the SAW element involved by embodiment 4.It addition, following condition only illustrates the difference of the SAW element with comparative example 1.

(simulated conditions of embodiment 4)

[IDT electrode 3]

The electrode of IDT electrode 3 refers to 32:

The electrode of end regions 3b refers to the radical of 32: (from the end of IDT electrode 3) 20

The electrode of end regions 3b refers to the dutycycle of 32: the electrode of main region 3a refers to dutycycle × 0.86 of 32

[reflector 4]

Spacing Pt2: the 1 spacing Pt1a × 1.02 of reflector electrode 42

The result of the SAW element of the embodiment 4 calculated according to the condition of such emulation shown in Figure 25.Curve chart shown in Figure 25 represents frequency at transverse axis, represents absolute value | Z | of impedance or the phase place of impedance at the longitudinal axis.Additionally, Figure 25 (b) is the figure part surrounded by the single dotted broken line of Figure 25 (a) being exaggerated.It addition, in the simulation, the dutycycle being positioned at the IDT electrode 3 of end regions 3b is made all to there occurs change.

Even if when so making the dutycycle being positioned at the IDT electrode 3 of end regions 3b there occurs change, it is also possible to similarly to Example 3, reduce the parasitism of longitudinal mode, and reduce the parasitism of the impedance produced before and after 890MHz in comparative example 1.

In the explanation of the above embodiment comprising embodiment 1 to embodiment 4, as the method making the resonant frequency of reflector 4 change, it is illustrated for making the spacing Pt2 method changed, but as additive method, it is possible to make method that the dutycycle of reflector electrode 42 changes, 32 refer to the thickness s of 42 method etc. changed with reflector electrode to make electrode refer to.When being made the resonant frequency of reflector 4 change by the method beyond spacing Pt2, if when the 1st spacing Pt1a of IDT electrode 3 being set as the half-wavelength of wavelength X of elastic wave, then spacing pt2 being set as and the 1st spacing Pt1a same degree.At this, wavelength X (2 × Pt2) is such as 1.5 μm～6 μm.

Additionally, in the present embodiment, illustrate only design parameter (radical, cross width, spacing, dutycycle, the thickness of electrode, the frequency etc.) situation about determining referring to design as electrode, but no matter the present invention all can obtain for the SAW element of which type of parameter and reduce parasitic effect.Such as confirmed by emulating, even if from the example of embodiment 1 make radical that the electrode of IDT electrode refers to, cross width there occurs change time, also be able to play good Spurious suppression effect by the position (radical from end) of change section 300 similarly to Example 1, clearance G p (the 1st clearance G p1, the 2nd clearance G p2).

And then, in embodiment 1, except the 2nd clearance G p2 is adjusted to setting, it is also possible to the electrode based on end regions 3b is referred to, and the resonant frequency of design is set as referring to that the resonant frequency of design is high than the electrode based on main region 3a.By so the electrode based on end regions 3b being referred to that the resonant frequency of design is set to higher such that it is able to obtain the effect same with when setting aforesaid 2 clearance G p2, it is possible to reduce the parasitism of longitudinal mode further.

Resonant frequency in order to will be located in the IDT electrode 3 of end regions 3b is set as higher than the resonant frequency of the IDT electrode 4 being positioned at main region 3a, as long as reducing the 2nd spacing Pt1b of the IDT electrode 3 being positioned at end regions 3b.The 2nd spacing Pt1b being positioned at the IDT electrode 3 of end regions 3b is such as set as that relative to the 1st spacing Pt1a of the IDT electrode 3 being centrally located region 3a be more than 0.986 times and the scope less than 1 times.By such composition such that it is able to further electrode to be referred to that A and reflector electrode refer to that the distance of C is set to desired relation.

In wave filter, channel-splitting filter, multiple resonators of various radicals, cross width are combined and play characteristic, and using the SAW element of the present invention as resonator use time, it is possible to for above-mentioned multiple resonators, set the design load of IDT electrode and reflector.Therefore, even if use the SAW element of the present invention in wave filter, channel-splitting filter, it is also possible to be designed in the same manner as using the situation of existing elastic wave device.

Additionally, when changing the design parameter beyond radical, cross width (frequency, thickness of electrode etc.), the position (radical m from end) of change section 300, clearance G p etc. are suitably set as optimum.For this, employing employs the emulation of Mode Coupling method (COM (Coupling-Of-Modes) method).Specifically, after the design parameter devising resonator, emulate by making the position (radical m from end) of change section 300, clearance G p etc. change such that it is able to it is found that reduce the condition of parasitism well.

Although the electrode constituting end regions 3b refers to according to the electrode constituting IDT electrode 3, the radical m of 32 refers to that total radical of 32 exists desirable radical, but this can determine by employing the emulation of COM method.Even if additionally, not being that this desirable radical also is able to reduce parasitism.Refer in the scope of total radical (about 50 to 500) of 43 at the electrode of the composition IDT electrode 3 being typically designed as SAW element 1, it has been acknowledged that radical m is obtained in that good characteristic in the degree from 5 to 20.

Figure 16 indicates that the block diagram of the major part of the communicator 101 involved by embodiments of the present invention.Communicator 101 carries out make use of the radio communication of electric wave.Channel-splitting filter 7 has the function that the signal of transmission frequency and the signal receiving frequency carry out partial wave in communicator 101.

In communicator 101, comprise the information that should send send information signal TIS be modulated by RF-IC103 and the raising (conversion to the high-frequency signal of carrier frequency) of frequency and become transmission signal TS.Send signal TS and removed the unwanted contributions beyond the passband sent by band filter 105, and be amplified by amplifier 107 and be input to channel-splitting filter 7.Channel-splitting filter 7 is removed the unwanted contributions beyond the passband sent signal TS from sending of inputting and is exported antenna 109.Antenna 109 converts the signal of telecommunication (sending signal TS) inputted to wireless signal and is transmitted.

In communicator 101, the wireless signal received by antenna 109 is converted to the signal of telecommunication (receiving signal RS) by antenna 109 and is input to channel-splitting filter 7.Channel-splitting filter 7 is removed the unwanted contributions beyond the passband received signal RS from receiving of inputting and is exported amplifier 111.The reception signal RS exported is amplified by amplifier 111, and is removed the unwanted contributions beyond the passband received by band filter 113.Then, receive signal RS to be carried out the reduction of frequency and demodulation by RF-IC103 and become reception information signal RIS.

It addition, sending information signal TIS and reception information signal RIS can be the low frequency signal (baseband signal) comprising suitable information, for instance the acoustical signal of emulation or digitized acoustical signal.The passband of wireless signal can make to follow the frequency band of the various standards such as UMTS (UniversalMobileTelecommunicationsSystem, UMTS).Modulation system can be any one of phase-modulation, Modulation and Amplitude Modulation, frequency modulation(PFM) or their combinations of any more than 2.

Figure 17 indicates that the circuit diagram of the composition of the channel-splitting filter 7 involved by one embodiment of the present invention.Channel-splitting filter 7 is the channel-splitting filter 7 that in Figure 16, communicator 101 uses.SAW element 1 is such as the SAW element of the ladder type filter circuit constituting the transmitting filter 11 in the channel-splitting filter 7 shown in Figure 16.

As shown in figure 17, transmitting filter 11 has piezoelectric substrate 2 and the series resonator S1～S3 formed on piezoelectric substrate 2 and parallel resonator P1～P3.

Channel-splitting filter 7 main by antenna terminal 8, send terminal 9, receiving terminal 10, be configured at antenna terminal 8 and the transmitting filter 11 sent between terminal 9 and the receiving filter 12 that is configured between antenna terminal 8 and receiving terminal 10 is constituted.

Transmission signal TS from amplifier 107 is input to transmission terminal 9, is input to the signal TS that sends sending terminal 9 and removes the unwanted contributions beyond the passband sent in transmitting filter 11 and export antenna terminal 8.Additionally, input receives signal RS from antenna 109 to antenna terminal 8, in receiving filter 12, remove the unwanted contributions beyond the passband received and export receiving terminal 10.

Transmitting filter 11 is such as made up of ladder type SAW filter.Specifically, transmitting filter 11 has: 3 series resonator S1, S2, the S3 being connected in series between its input side and outlet side；And 3 parallel resonators P1, P2, P3 being arranged between the series arm as the wiring for series resonator is connected to each other and reference potential portion G.That is, transmitting filter 11 is the ladder type filter of 3 level structures.But, in transmitting filter 11, the progression of ladder type filter is arbitrary.

Between parallel resonator P1～P3 and reference potential portion G, it is provided with inducer L.By the inductance of this inducer L is set as prescribed level, thus forming attenuation pole outside the passband sending signal and increasing attenuation outside a channel.The each free SAW resonator of multiple series resonator S1～S3 and multiple parallel resonator P1～P3 is constituted.

Receiving filter 12 such as has multi-mode type SAW filter 17 and is connected in series in the auxiliary resonator 18 of its input side.It addition, in the present embodiment, multi-mode comprises double mode.Multi-mode type SAW filter 17 has balanced-unbalanced translation function, and receiving filter 12 is connected with 2 receiving terminal 10 of output balanced signal.Receiving filter 12 is not limited to be made up of multi-mode type SAW filter 17, it is also possible to be made up of ladder type filter, it is also possible to be the wave filter without balanced-unbalanced translation function.

Between the junction point and earthing potential portion G of transmitting filter 11, receiving filter 12 and antenna terminal 8, it is also possible to insert the circuit of the impedance matching being made up of inducer etc..

By using above-mentioned SAW element 1 as the SAW resonator of such channel-splitting filter 7 such that it is able to improve the filter characteristic of channel-splitting filter 7.It is applied to the filter characteristic of the channel-splitting filter of the situation of the series resonator S1～S3 of transmitting filter 11 for the SAW element 1 of the structure of the SAW element by employing embodiment 1, has calculated by emulating.It addition, the passband of channel-splitting filter 7 contemplates the sending side of the Band2 of UMTS.This result shown in Figure 18.In the curve chart shown in Figure 18, transverse axis represents frequency (MHz), and the longitudinal axis represents by characteristic (dB).Additionally, dotted line represents the filter characteristic of the situation of the SAW element employing comparative example 1, solid line represents the filter characteristic of the situation of the SAW element 1 employing embodiment 1.From the result shown in Figure 18 it can be seen that in the passband of sending side, what improve the frequency band lower than 1860MHz passes through characteristic.

In the so-called ladder type filter used at the sending side wave filter as the channel-splitting filter 7 shown in Figure 17, the resonant frequency of series resonator S1～S3 is set near the central authorities of filter passband.Additionally, the anti-resonance frequency of parallel resonator P1～P3 sets near the central authorities of filter passband.When adopting the configuration of such frequency and the elastic wave device of the present invention being used for series resonator S1～S3, it is possible to improve the loss near the central authorities of filter passband, fluctuation.

Additionally, in SAW element 1, as shown in Figure 7 and Figure 8, the parasitic peak (producing near 960MHz in Fig. 7 (a)) produced at the high frequency side higher than anti-resonance frequency is shifted over (being displaced-10MHz in Fig. 8 (a) near 950MHz) to more lower frequency side.To this, it is believed that with making the resonant frequency of reflector reduce, to lower frequency side, the working band of reflector there occurs that displacement is one of reason.The SAW element 1 of this situation parasitism owing to producing at the working band end periphery of reflector, thus while the electrical characteristic near resonant frequency is improved, but the loss in the high-frequency region higher than anti-resonance frequency worsens sometimes on the contrary.

In ladder type filter, in parallel resonator P1～P3, the frequency that this loss worsens is in the high high frequency side superposition of the central authorities than filter passband.Therefore, if using SAW element 1 as the parallel resonator of ladder type filter, then due to design, the loss of wave filter sometimes can be made on the contrary to worsen.Therefore, in ladder type filter, by only SAW element 1 being used for a part for series resonator such that it is able to while reducing the deterioration of filter characteristic, significantly improve and pass through characteristic.It addition, when be designed the anti-resonance frequency of the parallel resonator so that ladder type filter not in the passband of wave filter, it is possible to SAW element 1 is used as parallel resonator.

Symbol description

1 elastic wave device (SAW element)

2 piezoelectric substrates

2A upper surface

3 exciting electrodes (IDT electrode)

3a main region

3b end regions

30 comb electrodes

30a the 1st comb electrodes

30b the 2nd comb electrodes

31 busbars

31a the 1st busbar

31b the 2nd busbar

32 electrodes refer to

32a the 1st electrode refers to

32b the 2nd electrode refers to

300 change section

Pt1 spacing

Pt1a the 1st spacing

Pt1b the 2nd spacing

Gp gap

Gp1 the 1st gap

Gp2 the 2nd gap

4 reflectors

41 reflector busbars

42 reflector electrodes refer to

Pt2 spacing

5 protective layers

7 channel-splitting filters

8 antenna terminals

9 send terminal

10 receiving terminal

11 transmitting filters

12 receiving filters

15 conductive layers

17 multi-mode type SAW filter

18 auxiliary resonator

101 communicators

103RF-IC

105 band filters

107 amplifiers

109 antennas

111 amplifiers

113 band filters

S1, S2, S3 series resonator

P1, P2, P3 parallel resonator

Claims

1. an elastic wave device, possesses:

Piezoelectric substrate；

Exciting electrode, it is positioned at the upper surface of this piezoelectric substrate, has multiple electrode and refers to, is used for producing elastic wave；With

2 reflectors, it is positioned at the upper surface of described piezoelectric substrate, has multiple reflector electrode and refers to, clips described exciting electrode on the direction of propagation of described elastic wave,

Described exciting electrode has: be positioned at described elastic wave the direction of propagation both ends between the electrode that refers to of described electrode refer to the main region that design is the same；With refer to, from electrode, the position that design is modulated with this main region continue to end, clip described main region and be positioned at 2 end regions of both sides,

For described reflector, described reflector electrode the electrode referred to refers to than the electrode referred to by the described electrode of described main region, the resonant frequency that design determines refers to that the resonant frequency that design determines is low,

If the interval at the center that the center referred to by electrode described in described main region and the described electrode being adjacent refer to is set to a, the quantity that the described electrode constituting described end regions refers to is set to m, the described reflector electrode of the center that the described electrode near described end regions side among being referred to by the described electrode of described main region refers to and described reflector refer among the distance at center that refers to of the described reflector electrode near described end regions side be set to x, then meet

0.5 × a × (m+1) < x < a × (m+1).

2. elastic wave device according to claim 1, wherein,

Multiple described electrodes refer to that having multiple 1st electrode refers to refer to multiple 2nd electrodes,

Described exciting electrode has: have the 1st comb electrodes that the plurality of 1st electrode refers to；Refer to, with the plurality of 1st electrode, the 2nd comb electrodes that the plurality of 2nd electrode engaged refers to having.

3. elastic wave device according to claim 1 and 2, wherein,

2nd gap is less than the 1st gap, the gap that 2 described electrodes that described 1st gap is adjacent in described main region refer to, described 2nd gap be the described electrode near described end regions side among the described electrode of described main region refers to refer to and the described electrode of described end regions that is adjacent refer among the gap that refers to of the described electrode near described main region side.

4. elastic wave device according to claim 3, wherein,

Described 2nd gap is more than 0.87 times and less than 1 times relative to described 1st gap.

5. elastic wave device according to claim 1 and 2, wherein,

The described electrode of described end regions refer among the width that refers to less than the described electrode in described main region of the width that refers to of the described electrode near described main region side.

6. elastic wave device according to claim 5, wherein,

The described electrode of described end regions refer among the width that refers to of the described electrode near described main region side, be more than 0.877 times and less than 1 times relative to the width that described 1st electrode refers to or described 2nd electrode refers in described main region.

7. the elastic wave device according to any one of claim 1～6, wherein,

For described reflector, the interval at center that described reflector electrode refers to and the center that the described reflector electrode being adjacent refers to, the interval at the center that the center referred to more than the described electrode in described main region and the described electrode being adjacent refer to.

8. elastic wave device according to claim 1 and 2, wherein,

For described end regions, described electrode the electrode referred to refers to than the electrode referred to by the described electrode of described main region, the resonant frequency that design determines refers to that the resonant frequency that design determines is high.

9. elastic wave device according to claim 8, wherein,

1st is smaller than the 2nd spacing, the interval at the center that described 1st spacing is the center that refers to of electrode described in described end regions and the described electrode that is adjacent refers to, the interval at the center that described 2nd spacing is the center that refers to of the described electrode in described main region and the described electrode that is adjacent refers to.

10. elastic wave device according to claim 9, wherein,

Described 1st spacing of described exciting electrode is more than 0.986 times and less than 1 times relative to described 2nd spacing.

11. the elastic wave device according to any one of according to Claim 8～10, wherein,

For described exciting electrode, it is positioned at the width that the width that the described electrode of described end regions refers to refers to less than the described electrode being positioned at described main region.

12. the elastic wave device according to claim 3 or 4, wherein,

The gap that 2 described electrodes adjacent in described end regions refer to is equal with described 1st gap.

13. a channel-splitting filter, possess antenna terminal, be filtered and export the transmitting filter of described antenna terminal and to receiving the receiving filter that is filtered of signal from described antenna terminal to sending signal, wherein,

Described transmitting filter or described receiving filter have the elastic wave device according to any one of claim 1～12.

14. channel-splitting filter according to claim 13, wherein,

Described transmitting filter has the series resonator being connected in series respectively and the parallel resonator being connected in parallel relative to this series resonator, and at least some of of described series resonator is made up of described elastic wave device.

15. channel-splitting filter according to claim 13, wherein,

For described transmitting filter, only described series resonator is made up of described elastic wave device.

16. a communicator, possess:

Antenna；

The channel-splitting filter according to any one of claim 13～15 being connected with this antenna electric；With

The RF-IC electrically connected with this channel-splitting filter.